The present invention relates to medical devices generally, and to storing, delivering and positioning radioactive ribbons or wires into the body of a patient, which are commonly used in radiation oncology and intravascular radiotherapy. In particular, the present invention relates to such devices, often referred to as xe2x80x9cpigsxe2x80x9d or xe2x80x9cafterloaders.xe2x80x9d Such devices advance a ribbon having a radioactive source at its distal end along a catheter previously positioned within the body of a patient for a predetermined period of time, and which later withdraw the ribbon from the patient.
Restenosis after arterial intervention in general, and after percutaneous transluminal coronary angioplasty (xe2x80x9cPTCAxe2x80x9d) in particular, is a concern of physicians practicing PTCA today. Conventional PTCA is performed using a standard balloon catheter such as the type described in U.S. Pat. No. 5,304,197 entitled xe2x80x9cBalloons For Medical Devices And Fabrication Thereof,xe2x80x9d issued to Pinchuk et al. on Apr. 19, 1994, which is incorporated into this disclosure by reference. Balloon catheters are typically used with a guidewire which is inserted into the patient""s artery until its distal end is advanced past the diseased or stenotic area of the vessel, where there is a buildup of material. Balloon catheters typically have a guidewire lumen so that the proximal end of the guidewire can be inserted into the distal end of the balloon catheter. Thereafter, the balloon catheter is advanced over the guidewire until the balloon is adjacent the buildup of material, and the balloon is then inflated to compress the buildup. Finally, the balloon is deflated and the catheter is pulled back through the guidewire and removed from the patient""s vasculature.
Restenosis of the artery may occur after this procedure, such that the same area of the vessel collapses or becomes clogged again. Recent technology has discovered that treating the diseased area of the vessel with radiation after balloon angioplasty may help prevent restenosis.
Such technology is described in U.S. Pat. No. 5,199,939 issued to Dake et al. on Apr. 6, 1993, entitled xe2x80x9cRadioactive Catheter,xe2x80x9d which is incorporated into this disclosure by reference. Prior technology contemplates the delivery of unspecified doses of radiation via wires having radioactive distal tips. A catheter was inserted into the vasculature and advanced to the site of the previous angioplasty. The radioactive source wire would then be advanced through a lumen in the catheter, so that its radioactive tip is adjacent the diseased site and can deliver the requisite amount of radiation. Thereafter the catheter and wire were removed. Such a device is described in PCT Application PCT/US94/04857, entitled xe2x80x9cRadioactive Source Wire, Apparatus And Treatment Methods,xe2x80x9d published on Nov. 10, 1994 as WO 94/25106.
Because the intensity of the radiation delivered to the vessel wall varies in inverse proportion to the square of the distance between the radioactive source and the vessel wall, it is desirable to center the radioactive wire within the vessel. This is also true when exposing a vessel to a light source. Centering thus prevents areas of the vessel from being overexposed or underexposed to the radiation. One such way to center the radioactive wire would be to deliver the wire to the site via a central lumen of a spiral balloon catheter. An example of a spiral catheter is given in U.S. Pat. No. 4,762,130 issued to Fogarty et al. on Aug. 9, 1988, entitled xe2x80x9cCatheter With Corkscrew-Like Balloon,xe2x80x9d which is incorporated into this disclosure by reference.
It will be appreciated from the foregoing that, in order to accurately position the source wire or ribbon within the patient is desirable. It is also desirable to store the radioactive wire safely when not in use, and to deliver it upon demand. It is known in the medical field of oncology to use afterloader devices in the treatment of cancerous tumors using radioactive sources. Typically one or more catheters are positioned in the patient and then attached to the afterloader, which advances the radioactive source wire along the catheters according to a predetermined sequence calculated to deliver a therapeutic dose of radiation to the tumor. Examples of afterloaders can be found in U.S. Pat. Nos. 5,865,720, Feb. 2, 1999; 5,857,956, Jan. 12, 1999; 5,092,834, Mar. 3, 1992; all of which are incorporated into this disclosure by reference.
The present invention provides for an improved source wire delivery system, or afterloader, which is especially useful for Intravascular Radiation Therapy,(xe2x80x9cIRTxe2x80x9d).
The functions of the delivery device include providing for the safe storage, deployment, and retrieval of a ribbon containing radioactive elements. The device provides for the attachment of a special intravascular radiation therapy catheter, through which a drive mechanism extends and retracts the ribbon. In the unlikely event this mechanism fails during retrieval, stranding the radioactive elements outside the containment area, an alternative means of retrieving the ribbon is available. Additional features include a mechanism to restrict unauthorized access and a means to immobilize the ribbon during the treatment period.